var dns = require("dns");
dns.lookup("www.github.com", function onLookup(err, address, family) {
    console.log("ip地址：" + address);

    dns.reverse(address, function (err, hostnames) {
        if (err) {
            console.log(err.stack);
        }
        console.log("反向解析；" + address + "; " + JSON.stringify(hostnames));
    });
});